Other Comprehensive Income and Accumulated Other Comprehensive Income (details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Accumulated other comprehensive income [Roll Forward]
Accumulated other comprehensive income, net of tax, balance, beginning of year	$ 810	$ 2,236
Other comprehensive income (loss) before reclassifications	310
Amounts reclassified from accumulated other comprehensive income	7
Other comprehensive income (loss), net of taxes	317	(310)
Accumulated other comprehensive income, net of tax, balance, end of period	1,127	1,926
Changes in net unrealized gains on investment securities having no credit losses recognized in the consolidated statement of income	537	(376)
Changes in net unrealized gains on investment securities having credit losses recognized in the consolidated statement of income	2	9
Net changes in benefit plan assets and obligations	15	28
Net changes in unrealized foreign currency translation	(43)	(96)
Other comprehensive income (loss) before income taxes	511	(435)
Income tax expense (benefit), other comprehensive income (loss)	194	(125)
Changes in Net Unrealized Gains on Investment Securities Having No Credit Losses Recognized in the Consolidated Statement of Income [Member]
Accumulated other comprehensive income [Roll Forward]
Accumulated other comprehensive income, net of tax, balance, beginning of year	1,125
Other comprehensive income (loss) before reclassifications	354
Amounts reclassified from accumulated other comprehensive income	(3)
Other comprehensive income (loss), net of taxes	351	(245)
Accumulated other comprehensive income, net of tax, balance, end of period	1,476
Changes in net unrealized gains on investment securities having no credit losses recognized in the consolidated statement of income	537	(376)
Income tax expense (benefit), other comprehensive income (loss)	186	(131)
Changes in Net Unrealized Gains on Investment Securities Having Credit Losses Recognized in the Consolidated Statement of Income [Member]
Accumulated other comprehensive income [Roll Forward]
Accumulated other comprehensive income, net of tax, balance, beginning of year	197
Other comprehensive income (loss) before reclassifications	(1)
Amounts reclassified from accumulated other comprehensive income	2
Other comprehensive income (loss), net of taxes	1	6
Accumulated other comprehensive income, net of tax, balance, end of period	198
Changes in net unrealized gains on investment securities having credit losses recognized in the consolidated statement of income	2	9
Income tax expense (benefit), other comprehensive income (loss)	1	3
Net Benefit Plan Assets and Obligations Recognized in Shareholders' Equity [Member]
Accumulated other comprehensive income [Roll Forward]
Accumulated other comprehensive income, net of tax, balance, beginning of year	(431)
Amounts reclassified from accumulated other comprehensive income	8
Other comprehensive income (loss), net of taxes	8	18
Accumulated other comprehensive income, net of tax, balance, end of period	(423)
Net changes in benefit plan assets and obligations	15	28
Income tax expense (benefit), other comprehensive income (loss)	7	10
Net Unrealized Foreign Currency Translation [Member]
Accumulated other comprehensive income [Roll Forward]
Accumulated other comprehensive income, net of tax, balance, beginning of year	(81)
Other comprehensive income (loss) before reclassifications	(43)
Other comprehensive income (loss), net of taxes	(43)	(89)
Accumulated other comprehensive income, net of tax, balance, end of period	(124)
Net changes in unrealized foreign currency translation	(43)	(96)
Income tax expense (benefit), other comprehensive income (loss)		$ (7)